Tahiti: The First Direct3D 11.1 GPU

One of the many changes coming in Windows 8 next year will be the next iteration of Direct3D, which will be Direct3D 11.1. More so than any other version of Direct3D so far, D3D11.1 is best summed up as a housekeeping release. There will be some new features, but compared to even past point releases such as 10.1 and 9c it’s a small release that’s going to be focusing more on improving the API itself – particularly interoperability with SoC GPUs for Windows 8 – than it will be about introducing new features. This is largely a consequence of the growing length of time for all matters of development hardware and software. By the time Windows 8 ships Direct3D 11 will be 3 years old, but these days that’s shorter than the development period for some AAA games. Direct3D 11/11.1 will continue to be the current Windows 3D API for quite some time to come.

With regards to backward compatibility in D3D11.1, there’s one new feature in particular that requires new hardware to support it: Target Independent Rasterization. As a result AMD’s existing D3D11 GPUs cannot fully support D3D11.1, thereby making Tahiti the first D3D 11.1 GPU to be released. In practice this means that the hardware is once again ahead of the API, even more so than what we saw with G80 + D3D10 or Cypress (5870) + D3D11 since D3D11.1 isn’t due to arrive for roughly another year. For the time being Tahiti’s hardware supports it but AMD won’t enable this functionality until the future – the first driver with D3D11.1 support will be a beta driver for Windows 8, which we expect we’ll see for the Windows 8 beta next year.

So what does D3D11.1 bring to the table? The biggest end user feature is going to be the formalization of Stereo 3D support into the D3D API. Currently S3D is achieved by either partially going around D3D to present a quad buffer to games and applications that directly support S3D, or in the case of driver/middleware enhancement manipulating the rendering process itself to get the desired results. Formalizing S3D won’t remove the need for middleware to enable S3D on games that choose not to implement it, but for games that do choose to directly implement it such as Deus Ex, it will now be possible to do this through Direct3D.

S3D related sales have never been particularly spectacular, and no doubt the fragmentation of the market is partially to blame, so this may be the push in the right direction that the S3D market needs, if the wider consumer base is ready to accept it. At a minimum this should remove the need for any fragmentation/customization when it comes to games that directly support S3D.

With S3D out of the way, the rest of the D3D11.1 feature set isn’t going to be nearly as visible. Interoperability between graphics, video, and compute is going to be greatly improved, allowing video via Media Foundation to be sent through pixel and compute shaders, among other things. Meanwhile target independent rasterization and some new buffer commands should give developers a few more tricks to work with, while double precision (FP64) support will be coming to pixel shaders on hardware that has FP64 support.

Finally, looking at things at a lower level D3D11.1 will be released alongside DXGI 1.2 and WDDM 1.2, the full combination of which will continue Microsoft’s long-term goal of making the GPU more CPU-like. One of Microsoft’s goals has to been to push GPU manufacturers to improve the granularity of GPU preemption, both for performance and reliability purposes. Since XP things have gotten better as Vista introduced GPU Timeout Detection and Recovery (TDR) to reset hung GPUs, and a finer level of granularity has been introduced to allow multiple games/applications to share a GPU without stomping all over each other, but preemption and context switches are still expensive on a GPU compared to a CPU (there are a lot of registers to deal with) which impacts performance and reliability.

To that end preemption is being given a bit more attention, as WDDM 1.2 will be introducing some new API commands to help manage it while encouraging hardware developers to support finer grained preemption. Meanwhile to improve reliability TDR is getting a major addition by being able to do a finer grained reset of the GPU. Currently with Windows 7 a TDR triggers a complete GPU reset, but with Windows 8 and WDDM 1.2 the GPU will be compartmentalized into “engines” that can be individually reset. Only the games/applications using a reset engine will be impacted while everything else is left untouched, and while most games and applications can already gracefully handle a reset, this will further reduce the problems a reset creates by resetting fewer programs.

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291 Comments

We'll have to see if amd "magically changes that number and informs Anand it was wrong like they did concerning their failed recent cpu.... LOLThat's a whole YEAR of lying to everyone trying to make their cpu look better than it's actual fail, and Anand shamefully chose to announce the number change "with no explanation given by amd"... - That's why you should be cautious - we might find out the transistor count is really 33% different a year from now.Reply

Not necessarily. The other possibility is that being 37% better on average at 1080P (from this Review) over HD6970 for $320 more than an HD6950 2GB that can unlock into a 6970 just isn't impressive enough. That should be d). Reply

I agree RS, as these amd people are constantly screaming price percentage increase vs performance increase... yet suddenly applying the exact combo they use as a weapon against Nvidia to themselves is forbidden, frowned upon, discounted, and called unfair.... Worse yet, according to the same its' all Nvidia's fault now - that amd is overpriced through the roof...LOL - I have to laugh. Also, the image quality page in the review was so biased toward amd that I thought I was going to puke.Amd is geven credit for a "perfect algorythm" that this very website has often and for quite some time declared makes absolutely no real world difference in games - and in fact, this very reviewer admitted the 1+ year long amd failure in this area as soon as they released "the fix" - yet argued everyone else was wrong for the prior year. The same thing appears here.Today we find out the GTX580 nvidia card has much superior anti-shimmering than all prior amd cards, and that finally, the 7000 high end driver has addressed the terrible amd shimmering.... Worse yet, the decrepit amd low quality impaired screens are allowed in every bench, with the 10% amd performance cheat this very site outlined them merely stated we hope Nvidia doesn't so this too - then allowed it, since that year plus ago... In the case of all the above, I certainly hope the high end 797x cards aren't CHEATING LIKE HECK still. For cripe sakes, get the AA stuff going, stop the 10% IQ cheating, and get our bullet physics or pay for PhysX, and stabilize the drivers .... I am sick of seeing praise for cheating and failures - if they are (amd) so great let's GET IT UP TO EQUIVALENCY ! Wow I'm so mad I don't have a 7970 as supply is short and I want to believe in amd for once... FOR THE LOVE OF GOD DID THEY GET IT RIGHT THIS TIME ?!!?Reply